custom css for site title in header

I would like to change the colour of each word in the site title with span tags.
I can't find where to do this. Nothing in Header.php

The reason: When I activate the Artiseer them in WP the logo in the header becomes all fuzzy. Something happens to the quality of the image between exporting from Artisteer and activating on WP. I resize the image in Photoshop as a high quality .jpg and it's good right up to after the theme's been activated.
Many thanks